Solar energy collection systems convert direct sunlight into thermal or electrical energy. Once such type of energy collection system is called a solar concentrator and uses curved mirrors to reflect and focus incident sunlight onto a solar converter such as a photocell or fluid pipe coupled to a heat exchanger.
Solar concentrators have an advantage over traditional flat solar panels in that fewer photocells are required to collect the energy. Whereas photocells are required over the entire surface of the solar panel, a concentrator only requires such photocells (or heat exchange system) at the focal point or axis of the concentrator mirror. While this reduces cost, it also imparts an inherent disadvantage within concentrator systems. That is, solar concentrators must be precisely oriented toward the sun in order to maintain a high efficiency of collection and this problem is compounded by the fact that the sun moves throughout the day.
Different solutions have been proposed for properly oriented the solar concentrator toward the sun. Some of these solutions—such as U.S. Pat. No. 3,996,460 (Smith), U.S. Pat. No. 6,274,862 (Rieger), U.S. Pat. No. 4,445,030 (Carlton), and U.S. Patent Application Publications 2004/0079863 (Lasich), 2008/0017784 (Hoot), and 2002/0179138 (Lawheed)—use light boxes, pinholes, shadow masks, shadow bars, and the like to detect off-axis orientation of the detectors relative to the sun. A drawback to these approaches is that, since the shadow-casting means in these references is part of the same structure as the detectors, a misalignment of the housing relative to the collector would cause an error when trying to align the mirror.
Accordingly, the need remains for an improved means for optimally orienting a solar concentrator toward the sun while avoiding the drawbacks of these prior systems.